1. Field of the Invention
The present invention relates to desalination plants for producing potable water, and particularly to a hydrogen-powered desalination plant that provides a multi-stage flash (MSF) desalination plant powered by carbon-free combustion of hydrogen.
2. Description of the Related Art
Desalination is a growing industry in many parts of the world. Both countries with vast areas of arid land and countries having more diverse climates are increasingly producing fresh water through desalination to meet the demands of growing populations and rising standards of living.
Several desalinating methods for seawater or brine have been developed, and may mainly be classified into two types. The first type is membrane isolation, such as reverse osmosis filtering or electrodialysis. The reverse osmosis method is suitable for desalinating seawater, and the electric dialysis is suitable for treating brine containing lesser quantities of salt. The second type is thermal separation. Thermal separation usually involves two cycles of evaporation followed by condensation. Reverse osmosis usually requires elevation of seawater pressure before introducing the seawater to the membrane separation system, while thermal separation typically requires elevating seawater temperature to start the thermal separation process.
Multi-stage flashing (MSF) and multistage effect evaporation (MEE) are the most developed thermal desalination technologies, Both processes require steam to heat up the seawater and elevate its temperature to start evaporation. For this reason, thermal desalination plants are usually coupled with separate power plants or steam generation plants, where low pressure steam is used to preheat seawater in the top brine heater before starting the desalination process. The heating steam is the exhaust of a conventional power turbine (or a back pressure turbine) in a simple steam power plant (Rankine cycle). The heating steam circulates in a closed loop between the power plant (steam generator) and the top brine heater of the desalination plant and works as an intermediate fluid to provide the needed heat to drive the top brine heater. The generation of heating steam undergoes a separate sequence of heating, expanding, condensing and pumping in the power plant. The top brine heater may be considered as a steam condenser for the power plant. The heating process takes place at a relatively low temperature (90° C.˜120° C.) to avoid salt precipitations and scale formation on the walls of the pipes carrying the heating steam. While such conventional power plants or steam generation plants are practical for providing the heat or steam needed to preheat the seawater, they are indirect processes, thus having low efficiency. Heating the brine using direct flame is more efficient. However, a direct flame produced by the combustion of hydrocarbon fuel cannot be used because it contains many non-condensable gases (CO2), toxic gases (NOx and CO), and unburned hydrocarbons, among other combustion products. Moreover, the combustion by-products and exhaust gases discharged from the power plants using hydrocarbon fuels are not environmentally friendly, and contribute to the greenhouse effect.
Thus, a hydrogen-powered desalination plant solving the aforementioned problems is desired.